Collapse Behaviours of Stiffened Panels Under Longitudinal Compression Considering Heating and Cooling Processes

Ming Cai Xu,Zhao Jun Song,Jin Pan 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.4

The fi re accidents casually happen during operation of ship, which would infl uence the load carrying capacity of stiff ened panel of ship structures due to the thermal load. The present paper aims to understand the infl uence of thermal loads on the collapse behaviour of stiff ened panels under longitudinal compressive load. Considering the heating and cooling down processes, the collapse behaviours of the stiff ened panels under combined in-plane displacement and heat loads representative of fi re accident are simulated in the FE (fi nite element) analysis herein. Firstly, the thermal load is considered to investigate the stress state of the stiff ened panels during heating and cooling processes. It is found that the stiff ened panels would collapse during thermal loads for the structure with large heated zone. After that, the longitudinal compression loads are applied to assess the collapse strength of the stiff ened panels. The parametric studies including diff erent geometrical dimensions and areas of heat zone are performed in detail to quantify the eff ects of heat loads on the collapse behaviours of stiff ened panels. It is found that the expansion could produce biaxial stress state that depends on not only in-plane stiff ness but also collapse modes, and for stiff ened panels with various heated area the cooling down to room temperature induce similar ultimate strength to that without considering heat loads.

A Proposed Procedure for Progressive Collapse Analysis of Common Steel Building Structures to Blast Loading

Meysam Bagheri Pourasil,Yaghoub Mohammadi,Amin Gholizad 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.6

There is rising concern among researchers regarding the suitability of structural design for abnormal load resistance. Abnormal loading generated by a blast or impact can cause local damage to a structure that could affect the entire structural system. Structures must be designed to prevent such disproportional consequences. Research has focused on progressive collapse analysis of buildings, most of which are based on the alternative path method and the sudden removal of one or several columns. In this procedure, failure of elements adjoining to the removed columns under blast conditions are ignored, which can lead to an incorrect prediction of progressive collapse. The present study developed a procedure for progressive collapse analysis of common steel building structures subject to blast loading. A 3D numerical model for direct simulation of blast loading is proposed to study the real behavior of a 7-story building under blast loading. A blast load equivalent to 1 t of TNT was simulated at a distance of 4 m from the corner of the structure to assess the direct effect on the structure. The pressure of this blast at 4 levels of loading was applied to adjacent structural members and the structural response was examined and the exciting forces in the adjacent structural members of the blast site were compared. The results indicate that the potential for progressive collapse when assuming blast loading as the initial cause of failure will differ from results of common methods used for evaluation of progressive collapse and in methods that ignore the initial reason for progressive collapse.

True Collapse Mechanisms of Two Dimensional Frames Determined from True Nonlinear Yield Surfaces

Fethullah Uslu,Mehmet Tevfik Bayer,Mustafa Haluk Saraçoğlu 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

In this work, collapse mechanisms and collapse load factors of two-dimensional frames which are subject to point loads and uniformly distributed loads are determined by employing new elastoplastic analysis method. In this new iterative method as the applied loads on frames are gradually increased, plastic hinges begin to develop at frame member sections and this continues until the partial or total collapse occurrence. If a plastic hinge develops at a section of a frame member, then a mechanical hinge is defined at this location and at each iteration reduced plastic moments are also applied as external loads. This is a new approach to search for the next plastic hinge where a series of linear elastoplastic analyses are executed. For each analysis the revised reduced plastic moments are used in the calculations. For elastoplastic calculations of two-dimensional frames, yield surface definitions of frame member sections are needed, and for I sections, yield surfaces are defined by two curves. In order to simplify collapse load factor calculations these yield surfaces are generally approximated by two lines. In this work the influences of the approximations on the elastoplastic behaviour of two-dimensional frames are examined by comparing the solutions of four example frames. When their solutions are compared, it is observed that almost equal collapse load factors are determined when true and approximate yield surfaces are used in the elastoplastic calculations but true collapse mechanisms are obtained only when true nonlinear yield surfaces are used.

외압을 받는 두꺼운 원통형 내압용기의 붕괴하중 해석

이재환,박병재 대한조선학회 2019 大韓造船學會 論文集 Vol.56 No.2

Number of studies on the buckling of thin cylindrical pressure vessels, such as submarine pressure hull and pipe with a large ratio of diameter/thickness, have been carried out in the naval and ocean engineering. However, research about thick cylinder pressure vessel has not been active except for the specific application in nuclear area. There are not many papers for the estimation of buckling and ultimate load capacity of thick cylinders for the deep sea usage. Thus, it is important to understand the theoretical bases of the buckling and collapse process and the derivation process of such loads for the proper design and structural analysis. The objective of this study is to survey the collapse behavior, to analyse and clarify the derivation procedure and to estimate the ultimate collapse load for thick cylinder by analyzing relevant books and papers. It is found that the yielding begins at the internal surface of the thick cylinder and plasticity develops from the internal surface to the external surface to generate collapse. Also the initial imperfection of cylinder develops flattening and consequently accelerates buckling and finally ultimate collapse. By comparing the collapse loads of aluminum thick cylinder by applying equations herein, it is shown that the equations analyzed are appropriate to obtain collapse load for thick cylinder.

ELS를 이용한 고층 RC 빌딩의 붕괴해석 및 발파해체해석 기법의 국부손상-연쇄붕괴 전이과정 해석에 응용

김현수 ( Hyon Soo Kim ),박훈 ( Hoon Park ),김승곤 ( Seung Kon Kim ),이연규 ( Yeon Gyu Lee ),조상호 ( Sang Ho Cho ) 대한화약발파공학회 2011 화약발파 Vol.29 No.2

Progressive collapse analyses of high-rise buildings subjected to abnormal loading such as fires, impacts, earthquakes, typhoon, bomb blasts etc. are intended. However it is difficult to perform collapse experiments of the real scale building to determine the capacity of the structure under an extreme loading events. In this study, collapse behavior of a 15 story RC structure building loaded by external explosion pressures were simulated using Extreme Loading Structures (ELS) software. The standoff distance between the RC building and explosives of 1500 kg was 1, 2, 5, 10, and 15 meters. The explosive demolition analysis techniques based on removal of partial support structures following blast scenario was adapted to investigate the transition process of progressive collapse-local damage.

Investigation of the Progressive Collapse in a Suspension Bridge Under the Explosive Load

Salar Farahmand-Tabar,Majid Barghian,Majid Vahabzadeh 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.6

Progressive collapse is a continuous spread of initial local failure from one member to another one, fi nally causing the collapse of the structure entirely or a disproportionately large part of it. This disproportionate collapse is due to the small initial local failure induced by unpredicted attacks, exhibiting that the structural system cannot resist the development of damage due to the insuffi cient load carrying capacity. In this study, a typical suspension bridge was modeled and analyzed under explosion load. For this purpose, diff erent scenarios were investigated. Forces and moments of the superstructure, responses and the stability of the structure under the applied loads were studied. Explosion applied on the structure depends on the amount of the load and local eff ects. Also, by removing one or several elements of structures, the force is distributed in the whole structure. For loading rate on diff erent positions of the structure, it was observed that the critical position would be under the explosion and towers adjacent. Towers adjacent and the middle of the deck were prone to the maximum infl uences where should be put more attention on and be reinforced to preserve the structure from the total and local failure.

An Adaptive Undervoltage Load Shedding Against Voltage Collapse Based Power Transfer Stability Index

Muhammad Nizam,Azah Mohamed,Aini Hussain 대한전기학회 2007 Journal of Electrical Engineering & Technology Vol.2 No.4

This paper highlights the comparison of a proposed methods named adaptive undervoltage load shedding based PTSI techniques for undervoltage load shedding and two previous methods named Fixed Shed Fixed Delay (FSFD) and Variable Shed Variable Delay (VSVD) for avoiding voltage collapse. There are three main area considerations in load shedding schemes as the amount of load to be shed, the timing of load shedding event, and the location where load shed is to be shed. The proposed method, named as adaptive UVLS based PTSI seem to be most appropriate among the uncoordinated schemes. From the simulation result can be shown the Adaptive UVLS based PTSI give faster response, accurate and very sensitive control for the UVLS control technique. This technique is effectively when calculating the amount to be shed. Therefore, it is possible to bring the voltage to the threshold value in one step. Thus, the adaptive load shedding can effectively reduce the computational time for control strategy.

An Adaptive Undervoltage Load Shedding Against Voltage Collapse Based Power Transfer Stability Index

Nizam, Muhammad,Mohamed, Azah,Hussain, Aini The Korean Institute of Electrical Engineers 2007 Journal of Electrical Engineering & Technology Vol.2 No.4

This paper highlights the comparison of a proposed methods named adaptive undervoltage load shedding based PTSI techniques for undervoltage load shedding and two previous methods named Fixed Shed Fixed Delay (FSFD) and Variable Shed Variable Delay (VSVD) for avoiding voltage collapse. There are three main area considerations in load shedding schemes as the amount of load to be shed, the timing of load shedding event, and the location where load shed is to be shed. The proposed method, named as adaptive UVLS based PTSI seem to be most appropriate among the uncoordinated schemes. From the simulation result can be shown the Adaptive UVLS based PTSI give faster response, accurate and very sensitive control for the UVLS control technique. This technique is effectively when calculating the amount to be shed. Therefore, it is possible to bring the voltage to the threshold value in one step. Thus, the adaptive load shedding can effectively reduce the computational time for control strategy.

Progressive Collapse Assessment of Multistory Reinforced Concrete Structures Subjected To Seismic Actions

Ahmed Elshaer,Hatem Mostafa,Hamed Salem 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

Progressive collapse is a catastrophic partial or total failure of a structure that mostly occurs when a structure loses a primary component like a column. Some international standards have started to consider progressive collapse resistance in various approaches. In this study, the ‘Unified Facilities Criterion’ guidelines were used in assessing the structure; these guidelines represent one of the codes that discuss progressive collapse using sophisticated approaches. Three-dimensional nonlinear dynamic analyses using the ‘Applied Element Method’ were performed for a structure that lost a column during a seismic action. A parametric study was made to investigate the effect of different parameters on progressive collapse. In this study, a primary structural component was assumed lost during an earthquake. The studied parameters were the location of the removed column in plan, the level of the removed column, the case of loading, and the consideration of the slabs. For the study cases, it was concluded that the buildings designed according to the Egyptian code satisfies the progressive collapse requirements stated by ‘Unified Facilities Criteria’ (UFC) guidelines requirements with a safety factor of 1.97. Also, it was found that losing a column during a seismic action is more critical for progressive collapse than under gravity load. Finally, this study elaborated the importance of considering the slab in progressive collapse analysis of multistory buildings in order to include the significant catenary action developed by the slabs.

Plastic collapse of tapered, tip-loaded cantilevered beams

Wilson, James F.,El-Esnawy, Nayer A. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.9 No.6

The plastic collapse loads and their locations are predicted for a class of tapered, initially curved, and transversely corrugated cantilevered beams subjected to static tip loading. Results of both closed form and finite element solutions for several rigid perfectly plastic and elastic perfectly plastic beam models are evaluated. The governing equations are cast in nondimensional form for efficient studies of collapse load as it varies with beam geometry and the angle of the tip load. Static experiments for laboratory-scale configurations whose taper flared toward the tip, complemented the theory in that collapse occurred at points about 40% of the beams length from the fixed end. Experiments for low speed impact loading of these configurations showed that collapse occurred further from the fixed end, between the 61% and 71% points. The results may be applied to the design of safer highway guardrail terminal systems that collapse by design under vehicle impact.